Infection with the filoviruses, in particular Zaire ebolavirus (ZEBOV), Sudan ebolavirus, or Marburg virus (MARV), causes severe hemorrhagic fever (HF) in humans and nonhuman primates that is often fatal. In addition to the sporadic outbreaks that have occurred in humans in Central Africa since 1976 and have caused more than 1,800 human infections with a lethality rate ranging from 53% to 90%, Ebola virus (EBOV) has also decimated populations of wild apes in this same region. At this time, there is no preventive vaccine or post-exposure treatment option available for human use. Much remains to be learned about these highly virulent viruses; however, important advances have been made over the last decade in understanding how filoviruses cause disease and in developing preventive vaccines that are protective in nonhuman primates. There still remains an urgent need to develop filovirus-specific post-exposure strategies to respond to future outbreaks of these viruses and to counter acts of bioterrorism.